A 21-year-old patient with slurred speech, sleepiness, and mydriasis is likely experiencing intoxication from which substance?

The symptoms of slurred speech, sleepiness, and mydriasis (dilated pupils) point towards intoxication from alcohol. In a clinical setting, alcohol intoxication is characterized by cognitive impairments and alterations in motor skills, which can manifest as slurred speech. The sleepiness can occur due to the depressant effects of alcohol on the central nervous system, where the individual may feel drowsy or lethargic.

Mydriasis is somewhat unusual in alcohol intoxication compared to other substances, but it can still occur. Various factors, including the individual’s environment and the presence of other substances, can also influence pupil diameter.

When considering other substances: cocaine typically causes increased alertness and pupil dilation but is less associated with sleepiness and slurred speech; heroin would cause sedation and pinpoint pupils rather than mydriasis; LSD generally leads to altered perceptions and visual hallucinations, along with pupil dilation, but does not typically result in slurred speech or sleepiness.

Thus, the combination of these symptoms strongly indicates that the patient is experiencing alcohol intoxication.